Autism is a neurodevelopmental disorder characterized by difficulties with social interaction and communication, and by restricted and repetitive behavior. Parents often notice signs during the first three years of their child’s life.
These signs often develop gradually, though some autistic children experience regression in their communication and social skills after reaching developmental milestones at a normal pace.
Autism is associated with a combination of genetic and environmental factors. Risk factors during pregnancy include certain infections, such as rubella, toxins including valproic acid, alcohol, cocaine, pesticides, lead, and air pollution, fetal growth restriction, and autoimmune diseases.
Controversies surround other proposed environmental causes; for example, the vaccine hypothesis, which has been disproven. Autism affects information processing in the brain and how nerve cells and their synapses connect and organize; how this occurs is not well understood.
Autism’s symptoms result from maturation-related changes in various systems of the brain. How autism occurs is not well understood. Its mechanism can be divided into two areas: the pathophysiology of brain structures and processes associated with autism, and the neuropsychological linkages between brain structures and behaviors.
The behaviors appear to have multiple pathophysiologies.
There is evidence that gut–brain axis abnormalities may be involved. A 2015 review proposed that immune dysregulation, gastrointestinal inflammation, malfunction of the autonomic nervous system, gut flora alterations, and food metabolites may cause brain neuroinflammation and dysfunction.
Several interventions have been shown to reduce symptoms and improve the ability of autistic people to function and participate independently in the community.
Behavioral, psychological, education, and/or skill-building interventions may be used to assist autistic people to learn life skills necessary for living independently, as well as other social, communication, and language skills. Therapy also aims to reduce challenging behaviors and build upon strengths. Some autistic adults are unable to live independently.
Many autistic people face significant obstacles in transitioning to adulthood. Compared to the general population autistic people are more likely to be unemployed and to have never had a job. About half of people in their 20s with autism are not employed.
People with autism tend to face increased stress levels related to psychosocial factors, such as stigma, which may increase the rates of mental health issues in the autistic population.
An autistic culture has developed, with some individuals seeking a cure and others believing autism should be accepted as a difference to be accommodated instead of cured.
Globally, autism is estimated to affect 24.8 million people as of 2015. In the 2000s, the number of autistic people worldwide was estimated at 1–2 per 1,000 people. In the developed countries, about 1.5% of children are diagnosed with ASD as of 2017, from 0.7% in 2000 in the United States.
It is diagnosed four-to-five times more often in males than females. The number of people diagnosed has increased dramatically since the 1960s, which may be partly due to changes in diagnostic practice.